Babcock Power Limited

John W Campbell

A boiler safety valve installation with a safety valve discharging relief steam through an upstand into a separately supported vent pipe. The upstand discharges through a belled nozzle approximately 30.degree. (0.5 steradian) included angle into the vent pipe thereby, on discharge of relief steam, inducing a sub-atmospheric pressure in the space intermediate the discharge nozzle and the vent pipe and lessening the risk of escape of steam at a sliding junction between the upstand and the vent pipe. In installation where the relief steam flow reaches supersonic velocity at discharge from the belled nozzle the vent pipe diameter is constricted by about 5%-10% at a zone downstream of the discharge nozzle to produce a shock front and reduce the velocity to sub-sonic, thereby reducing the frictional flow loss effects while economizing in vent pipe size without causing a build-up of back pressure in the space intermediate the discharge nozzle and the vent pipe.

Boiler safety valve installations

A power plant forced-flow boiler operative with water letdown wherein the letdown water is arranged to deliver heat to partly expanded steam passing through a steam reheater connected between two stages of a prime mover. The heating of steam in the reheater by letdown water will partly or wholly replace the use of live steam for such purpose so that the live steam will be available for driving the prime mover.

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Maidenhead, United Kingdom

John W Campbell